Insulin dependent diabetes is associated with degenerative changes of small blood vessels. The etiology of these micro-vascular changes remain uncertain and is controversial. The study proposed is designed to continue long term longitudinal studies of older children and young adults with diabetes to clarify the interrelationship between metabolic control of the diabetes and the time of appearance and rate of progression of the micro-vascular changes known to occur with the disease. Vascular changes have been determined in both normal and diabetic subjects of comparable ages by measuring with the electron microscope the thickness of the capillary basement membranes (CBMT) from muscle biopsies. Retinal studies also have been performed on many of these research patients to correlate the degree of CBMT with early vascular changes in the eye grounds. Retinal changes are reported to appear in most diabetic patients 15 to 20 years after the onset of clinical (overt) diabetes. Additional data are necessary from older post-pubescent diabetic subjects with diabetes for 8 or more years in order to provide a sufficient number of observations to verify statistically if there is a definite relationship between the degree of control of the diabetes. These serious vascular changes ultimately cause blindness, kidney failure and premature death in these relatively young patients with insulin dependent diabetes.